Solution:

SH

Explanation :
If you look closely, you will see that the first letter of every set is moving 6 alphabets forward while the second one is moving six alphabets backwards.

Solution:

The answer is 0.
As
6 / 7 = 42 but the answer is written as 2
3 / 9 = 27 but the answer is written as 7
8 / 2 = 16 but the answer is written as 6
If we look at the answers, the second digit has been used in the problem.
Now, as
4 / 5 = 20 and the second digit is 0, the answer is 0.

Solution:

6

Explanation:
5*6 + 2 = 31
=> 7*6 + 2 = 44

Solution:

30(sum of corner of triangle)

Solution:

20 (double of previous)

Solution:

43

Solution:

6

sum of opposite number is 21

Solution:

245

space them properly as 21 24 27 30 33 36 39 42 45 ?

Solution:

-20

Its a alternate series riddle
60 40 20 0 (?)
40 43 46 49 (+3)

Solution:

17

It is the sum of the two digits(9 + 8) in opposite quadrant.